Fig. 3. Dominance index of eight pairs of crayfish recorded during the pairing period (Fig. 1B). All aggressive and submissive behaviors that were recorded during the daily 30 min pairing were scored (attack, +2; approach, +1; retreat, –1; tailflip, –2) and presented as a percentage to show the degree of dominance between each dominant–subordinate pair (see equation in Materials and methods). The degree of dominance was higher in all dominant animals (filled squares) than in subordinate animals (open squares). The dominant animals in pairs 2 and 3 were dominant for shorter periods (2 days and 8 days, respectively, at the end of 14 days) because of status reversals.